Fram Strait

The Fram Strait is located between Greenland and Svalbard at about 79—80° N. About 500 km wide, it separates the Arctic Ocean to the north from the Greenland Sea to the south. With a sill depth of about 2200 m, it is the only deep passage between the Mediterranean Arctic Ocean and its surrounding oceans, thereby providing the most important exchange in terms of volume and energy. A major fraction of Arctic sea ice—about 3000 km3 per year—is advected into the North Atlantic through this passage.

The transport of surface water masses between the North Atlantic and the Arctic occurs in two major currents. The ice-free West Spitsbergen Current (WSC) in eastern Fram Strait has its roots in the Gulf Stream and North Atlantic Current and introduces warm (4°C) saline (salinity about 35 psu) Atlantic water far north into the Arctic, where it submerges north of Svalbard below the cold (-1.8°C) but less saline (below 33 psu) Polar Water. A large fraction of the WSC is deflected to the west and contributes to the southward-flowing Return Atlantic Current. The heat transported within the WSC causes a relatively mild climate on the west coast on Svalbard, which is ice-free nearly year-round. On the west flank of the Fram Strait, conditions are extremely different. Cold polar water with sea ice is transported south with the East Greenland Current (EGC) with current speeds highest close to the surface (about 20 cm s-1). The Polar Front, the borderline between the EGC and the WSC, is marked by strong horizontal and vertical gradients in water temperature, salinity, current speeds and directions, as well as sea ice concentrations.

The fluxes of sea water and sea ice through Fram Strait influence the heat and freshwater budget of the Arctic Ocean and North Atlantic. At 80° N, about 4-6 Sv (1 Sverdrup = 106 m3 s-i) are transported out of the Arctic within the EGC, while the northward transport by the WSC accounts for about 1-3 Sv. Changes in the current strengths are of crucial importance in understanding the annual, interannual, and decadal variability of the climate in the Northern Hemisphere and the Earth, as they partially control the thermohaline circulation of the world's ocean. Ongoing research projects in this area include measurements from satellites, ships, and moored instrumentation to determine, for example, the thickness of sea ice or current speeds in Fram Strait.

Apart from water masses, the Polar Front also separates ecosystems, which are dominated by Arctic and Atlantic species according to the hydrographical regime. Biological productivity on the western Arctic side of Fram Strait is generally lower than on the eastern Atlantic side because of the sea ice cover. An exception is the Northeast Water Polynya on the Greenlandic shelf. Local currents and wind fields open the ice pack each year leading to elevated phytoplankton productivity, which in turn enhances pelagic and benthic life. Highest concentrations of plankton as well as birds and marine mammals are found in the marginal ice zone at the Polar Front, induced by locally enhanced phyto-plankton growth from spring to autumn.

Rolf Gradinger

See also Arctic Ocean; Greenland Sea; North Atlantic Drift; Thermohaline Circulation

Further Reading

Aagaard, K., "Inflow from the Atlantic to the Polar Basin." In The Arctic Ocean: The Hydrographic Environment and the Fate of Pollutants, edited by L. Rey, London: Macmillan, 1982, pp. 69-81 Aagaard, K., C. Darnall & P. Greisman, "Year-long current measurements in the Greenland-Spitsbergen Passage." Deep Sea Research, 20 (1973): 743-746 Aagaard, K., E. Fahrbach, J. Meincke & J.H. Swift, "Saline outflow from the Arctic Ocean: its contribution to the deep waters of the Greenland, Norwegian, and Iceland Seas." Journal of Geophysical Research, 96 (1991): 20433-20441 Barthel, K.-G., "Relationship of food uptake and body components of Calanus finmarchicus, C. glacialis and C. hyper-boreus to particulate matter and water characteristics in Fram Strait." Polar Biology, 10 (1990): 343-350

Berner, H. & G. Wefer, "Clay-mineral flux in the Fram Strait and Norwegian Sea." Marine Geology, 116 (1994): 327-345 Gradinger, R.R. & M.E.M. Baumann, "Distribution of phyto-plankton communities in relation to the large-scale hydro-graphical regime in the Fram Strait." Marine Biology, 111

Gradinger, R., M. Spindler & J. Weissenberger, "On the structure and development of Arctic pack ice communities in Fram Strait: a multivariate approach." Polar Biology, 12

Hebbeln, D. & G. Wefer, "Effects of ice coverage and ice-rafted material on sedimentation in the Fram Strait." Nature, 350 (1991): 409-411 Hirche, H. J., M.E.M. Baumann, G. Kattner & R. Gradinger, "Plankton distribution and the impact of copepod grazing on primary production in Fram Strait, Greenland Sea." Journal of Marine Systems, 2 (1991): 477-494 Muench, R.D., M.G. McPhee, C.A. Paulson & J.H. Morison, "Winter oceanographic conditions in the Fram Strait-Yermak Plateau Region." Journal of Geophysical Research, 97 (1992): 3469-3483 Piepenburg, D., W.G. Ambrose Jr., A. Brandt, P.E. Renaud, M.J. Ahrens & P. Jensen, "Benthic community patterns reflect water column processes in the northeast water polynya (Greenland)." Journal of Marine Systems, 10 (1997): 467-482

Rudels, B., H.J. Friedrich & D. Quadfasel, "The Arctic circumpolar boundary current." Deep-Sea Research, 46 (1999): 1023-1062

Schlichtholz, P. & M.-N. Houssais, "An inverse modeling study in Fram Strait. Part I.: dynamics and circulation." Deep-Sea Research, 46 (1999): 1083-1135 Smith Jr., W.O., R.I. Brightman & B.C. Booth, "Phytoplankton biomass and photosynthetic response during the winterspring transition in the Fram Strait." Journal of Geophysical Research, 96 (1991): 4549-4554

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